Seasonal Climate Research Articles

Updating the breeding sites of Aedes aegypti (Diptera: Culicidae) in Camagüey, Cuba

Mosquito-borne diseases continue to be of significant public health concern in various parts of the world, facilitated by the adaptations that certain species, such as Aedes aegypti, have managed to develop. In order to update the bioecological knowledge of A. aegypti populations in a Health Area of Camagüey Province, Cuba, a comprehensive entomological survey was conducted both indoors and outdoors, covering the entire urban population, encompassing a total of 36,584 households. Aedes aegypti colonized 52 types of breeding sites, of which 15 were found to be permanent and suitable (29.0%), contributing 82.0% of the positivity. Low tanks were particularly prominent (43.0%). Positivity in natural breeding sites remained low (0.11%). Larvae were collected in habitats with high levels of eutrophication (17.30%), grouped in 28 positive breeding sites, accounting for 3.32% of the total number of positive sites. No differences were observed in the total number of positive breeding sites and capture locations between climatic seasons, indicating a consistent pattern of positivity throughout the study year, during which six types of breeding sites exceeded a 70% monthly repetitiveness. These results underscore the importance of vigilance and control measures to be undertaken by residents in their respective households.

Acoustic phenology of tropical resident birds differs between native forest species and parkland colonizer species

Most birds are characterized by a seasonal phenology closely adapted to local climatic conditions, even in tropical habitats where climatic seasonality is slight. In order to better understand the phenologies of resident tropical birds, and how phenology may differ among species at the same site, we used ~70 000 hours of audio recordings collected continuously for two years at four recording stations in Singapore and nine custom‐made machine learning classifiers to determine the vocal phenology of a panel of nine resident bird species. We detected distinct seasonality in vocal activity in some species but not others. Native forest species sang seasonally. In contrast, species which have had breeding populations in Singapore only for the last few decades exhibited seemingly aseasonal or unpredictable song activity throughout the year. Urbanization and habitat modification over the last 100 years have altered the composition of species in Singapore, which appears to have influenced phenological dynamics in the avian community. It is unclear what is driving the differences in phenology between these two groups of species, but it may be due to either differences in seasonal availability of preferred foods, or because newly established populations may require decades to adjust to local environmental conditions. Our results highlight the ways that anthropogenic habitat modification may disrupt phenological cycles in tropical regions in addition to altering the species community.

Climate forcing controls on carbon terrestrial fluxes during shale weathering

Climate influences near-surface biogeochemical processes and thereby determines the partitioning of carbon dioxide (CO2) in shale, and yet the controls on carbon (C) weathering fluxes remain poorly constrained. Using a dataset that characterizes biogeochemical responses to climate forcing in shale regolith, we implement a numerical model that describes the effects of water infiltration events, gas exchange, and temperature fluctuations on soil respiration and mineral weathering at a seasonal timescale. Our modeling approach allows us to quantitatively disentangle the controls of transient climate forcing and biogeochemical mechanisms on C partitioning. We find that ~3% of soil CO2 (1.02 mol C/m2/y) is exported to the subsurface during large infiltration events. Here, net atmospheric CO2 drawdown primarily occurs during spring snowmelt, governs the aqueous C exports (61%), and exceeds the CO2 flux generated by pyrite and petrogenic organic matter oxidation (~0.2 mol C/m2/y). We show that shale CO2 consumption results from the temporal coupling between soil microbial respiration and carbonate weathering. This coupling is driven by the impacts of hydrologic fluctuations on fresh organic matter availability and CO2 transport to the weathering front. Diffusion-limited transport of gases under transient hydrological conditions exerts an important control on CO2(g) egress patterns and thus must be considered when inferring soil CO2 drawdown from the gas phase composition. Our findings emphasize the importance of seasonal climate forcing in shaping the net contribution of shale weathering to terrestrial C fluxes and suggest that warmer conditions could reduce the potential for shale weathering to act as a CO2 sink.

Coastal Dune Vegetation Dynamism and Anthropogenic-Induced Transitions in the Mexican Caribbean during the Last Decade.

In the Mexican Caribbean, environmental changes, hydrometeorological events, and anthropogenic activities promote dynamism in the coastal vegetation cover associated with the dune; however, their pace and magnitude remain uncertain. Using Landsat 7 imagery, spatial and temporal changes in coastal dune vegetation were estimated for the 2011-2020 period in the Sian Ka'an Biosphere Reserve. The SAVI index revealed cover changes at different magnitudes and paces at the biannual, seasonal, and monthly timeframes. Climatic seasons had a significant influence on vegetation cover, with increases in cover during northerlies (SAVI: p = 0.000), while the topographic profile of the dune was relevant for structure. Distance-based multiple regressions and redundancy analysis showed that temperature had a significant effect (p < 0.05) on SAVI patterns, whereas precipitation showed little influence (p > 0.05). The Mann-Kendall tendency test indicated high dynamism in vegetation loss and recovery with no defined patterns, mostly associated with anthropogenic disturbance. High-density vegetation such as mangroves, palm trees, and shrubs was the most drastically affected, although a reduction in bare soil was also recorded. This study demonstrated that hydrometeorological events and climate variability in the long term have little influence on vegetation dynamism. Lastly, it was observed that anthropogenic activities promoted vegetation loss and transitions; however, the latter were also linked to recoveries in areas with pristine environments, relevant for tourism.

A Level 3 monthly gridded ice cloud dataset derived from 12 years of CALIOP measurements

Abstract. Clouds play important roles in weather, climate, and the global water cycle. The Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) onboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) spacecraft has measured global vertical profiles of clouds and aerosols in the Earth’s atmosphere since June 2006. CALIOP provides vertically resolved information on cloud occurrence, thermodynamic phase, and properties. We describe version 1.0 of a monthly gridded ice cloud product derived from over 12 years of global, near-continuous CALIOP measurements. The primary contents are monthly vertically resolved histograms of ice cloud extinction coefficient and ice water content (IWC) retrievals. The CALIOP Level 3 Ice Cloud product is built from the CALIOP Version 4.20 Level 2 5 km Cloud Profile product that, relative to previous versions, features substantial improvements due to more accurate lidar backscatter calibration, better extinction coefficient retrievals, and a temperature-sensitive parameterization of IWC. The gridded ice cloud data are reported as histograms, which provides data users with the flexibility to compare CALIOP’s retrieved ice cloud properties with those from other instruments with different measurement sensitivities or retrieval capabilities. It is also convenient to aggregate monthly histograms for seasonal, annual, or decadal trend and climate analyses. This CALIOP gridded ice cloud product provides a unique characterization of the global and regional vertical distributions of optically thin ice clouds and deep convection cloud tops, and it should provide significant value for cloud research and model evaluation. A DOI has been issued for the product: https://doi.org/10.5067/CALIOP/CALIPSO/L3_ICE_CLOUD-STANDARD-V1-00 (Winker et al., 2018).

Seasonal landscape variability advances Lantian hominin's recognition capacity to strategically adapt to changing environments

Environmental Variability Selection (EVS) is hypothesized for the emergence of early Homo (H.) sapiens with small lithic tools in Africa. Yet, it is unclear how the EVS works when a special hominin group with advanced small lithic tools evolved from the Asian H. erectus with expedient core and flake industry. Lantian loessland in southern Chinese Loess Plateau in North China preserves continuous and concentrated hominin fossil, faunal, pollen, stone tool, paleoclimate, and landform records for last 2 million years (Ma) and is an ideal place to test this hypothesis. We reanalyzed δ13C values of soil organic and inorganic carbon from 2 Lantian loess-paleosol records to partition seasonal climate and habitat changes with synthesized lithic, faunal, and pollen data to seek cluses. We found that Lantian Gongwangling and Chenjiawo H. erectus adapts to woodland-forest habitats, manufacturing Mode 1 stone artifacts foraging subtropical animals in warm and Paleoarctic animals in cool seasons on the low and medium-high rolling loessland, while more advanced Dali hominins adapt to certain steppe-shrubland habitats manufacturing diverse small-sized lithic tools to forage more open-habitat animals in all seasons on hilly landforms. We propose that co-evolution of seasonal habitat variability and changing local landforms in 2.0–0.2 Ma advances Dali hominin's cognitive capacity for strategically using landform morphology for subsistence and manufacture small stone tools for intercepting high fluxes of seasonal resources on highly variable loessland. Seasonal landscape variability and landform evolution is the key in the EVS for the evolution from Asian H. erectus to a more advanced hominin group or species.

Skillful seasonal prediction of Afro-Asian summer monsoon precipitation with a merged machine learning and large ensemble approach

Afro-Asian summer monsoon precipitation (AfroASMP) is the life blood of billions of people living in many developing countries covering West Africa and Asia. Its complex variabilities are always accompanied by natural disasters like floods, landslides and droughts. Reliable AfroASMP prediction several months in advance is valuable for not only decision-makers but also regional socioeconomic sustainability. To address the current predicament of the AfroASMP seasonal prediction, this study provides an effective machine-learning model (Y-model). Y-model uses the monsoon related big climate data for searching the potential predictors, encompassing atmospheric internal factors and external forcings. Only the predictors associated with significant anomalies in summer horizonal winds at 850 hPa over the monsoon domain are retained. These selected predictors are then reorganized into a large ensemble based upon different thresholds of four fundamental principles. These principles include the focused sample sizes, the relationships between predictors and predictand, the independence among predictors, and the extremities of predictors in the forecast year. Real-time predictions can be generated based on the ensemble mean of skillful members during an independent hindcast period. Y-model skillfully predicts four monsoon precipitation indices of AfroASMP during 2011–2022 at lead 4–12 months, correlation skills range from 0.58 to 0.90 and root mean square error skills are reduced by 11–53% compared to CFS v2 model at lead 1 month. This study offers an effective method for preprocessing predictors in seasonal climate prediction.

Ring- and diffuse-porous tree species coexisting in cold and humid temperate forest diverge in stem and leaf phenology

Leaf and stem phenology are critical drivers of tree growth patterns in seasonal climates, but the implications for species differences in radial stem growth dynamics are still poorly studied. In our study, we compared the leaf phenology and stem phenology with the underlying cell development as well as annual stem growth between five diffuse-porous (DP) and five ring-porous (RP) coexisting angiosperm species in cold and humid temperate forests. Our results show that RP species unfolded leaves later but initiated wood growth earlier compared to DP species. Yet, xylem vessel maturation in the stem started in June and was remarkably synchronized between DP and RP, which implies that species from both functional groups can effectively avoid vessel cavitation potentially triggered by late spring frost. DP species exhibited one peak in stem growth across the growing season reflecting a uniform vessel formation pattern. Instead, RP species exhibited two peaks in stem growth, with the first peak reflecting expansion of early-wood vessels and the second peak related to subsequent fiber and vessel proliferation in the late-wood. In general, species with a greater number of growth days from the start of cambium activity until full lignification of cells exhibited higher annual stem growth, regardless of species group. The observed differences in leaf and stem phenology between DP and RP species are discussed with respect to the adaptation potential of the two functional groups to changing climate conditions in cold and humid temperate forests.

Activity of bats (Chiroptera) in extensive livestock systems in the Colombian Caribbean

Introduction: Extensive cattle ranching in tropical dry forest areas (TDF) has caused the transformation of natural ecosystems and altered the behavior of associated organisms, generating variation in activity patterns. In bats, the activity pattern is affected by the composition and vegetation structure of the ecosystem, and by the climatic season (dry and rainy). Objetive: In this study, the effect of conventional management systems (CS) and silvopastoral (SPS) of extensive livestock management on the bat activity patterns in the Colombian Caribbean was determined. Methods: The activity pattern of bats in TDF fragments associated with CS and SPS was compared within an annual cycle. The daily activity patterns of 11 species with records of more than 10 days in within management systems were determined. Results: Greater bat activity was recorded during the rainy season. We found that although bats show behavioral adaptation to the different management systems, in TDF fragments associated with SPS there is greater bat activity throughout the year, compared to the activity recorded in CS. Species with higher energetic requirements and degree of specialization (Phyllostomus hastatus, P. discolor and Glossophaga soricina) modified their activity patterns between CS and SPS management types. Conclusion: The TDF fragments associated in SSP, due to the vegetation composition and structure, probably favor the constant supply of resources suitable for the bats assemblage stability.

Climate change, seasonality and household water security in rural Gambia: A qualitative exploration of the complex relationship between weather and water

Climate change could pose a threat to water security for many communities, particularly in settings where rainfall patterns are becoming more varied and there is higher frequency of extreme events, such as heavy rainfall and droughts. Understanding how rainfall affects water security—including water access, water quality and water use behaviours—can inform investment in more climate-resilient infrastructure and safeguard against future health risks. This study aims to explore how households in rural Gambia experienced water security in relation to seasonal rainfall patterns and extreme weather events. Data collection focused on two communities (Kiang West and Basse) with differing access to water infrastructure, within which some villages had greater access to groundwater sources, such as solar-powered boreholes, and others primarily used uncovered wells. 46 participants were interviewed in Spring 2022 using multiple qualitative methods, including in-depth interviews and transect walks. We found that people’s experience of water security and rainfall (including seasonal rainfall, drought and heavy rainfall) was complex and varied according to the primary household water source. Both dry and rainy season posed challenges to household water security in terms of quality and quantity. Households with access to more resilient infrastructure, such as solar-powered boreholes, discussed a shift in the relationship between weather and water security, where they were less vulnerable to water shortages during dry conditions compared to those using wells. However, these sources did not fully resolve water security issues, as they experienced water shortages during cloudy conditions. Extreme weather events, such as heavy rainfall, heightened perceived water issues, as these events sometimes damaged water infrastructure and contaminated water sources. Seasonal workloads, that were higher in the rainy season, also jeopardised water security, as this limited time for water collection. Increased investment in infrastructure, maintenance, water-treatment and behavioural change is required to mitigate the risks.

Examining the role of biophysical feedbacks on simulated temperature extremes during the Tinderbox Drought and Black Summer bushfires in southeast Australia

The Tinderbox Drought (2017–2019) was one of the most severe droughts recorded in Australia. The extreme summer air temperatures (>40 °C) combined with drought, contributed to the unprecedented Black Summer bushfires in 2019–20 over southeast Australia. Whilst the temperature extremes were largely driven by synoptic processes, it is important to understand to what extent interactions between land and atmosphere played a role. In this study, we use the WRF-LIS-CABLE land-atmosphere coupled model to examine the impacts of changes in leaf area index (LAI) and albedo by contrasting simulations with climatological and time-varying LAI and albedo. We analyse the impact of these biophysical feedbacks on temperature extremes and fire risk during the Tinderbox Drought and the Black Summer bushfires. Remote-sensing data showed a decrease in LAI (0.1–4.0 m2 m−2) over the three years of the drought along the southeast coast of Australia relative to the long-term climatology, while albedo increased inland (0.02–0.14). These changes in LAI and albedo were accompanied by an overall decrease in daily maximum temperature (Tmax) in the vast majority of interior regions (by ∼0.5 °C) and, in the 2019–20 summer, by a clear increase in Tmax in the coastal regions of up to ∼1 °C. Increased albedo explained most of the decreases in Tmax inland, whereas increases in Tmax along the coasts were mostly associated with LAI declines. The magnitude of the impact of biophysical changes on temperature demonstrates the potential impact that would be missed in simulations that assumed fixed vegetation properties. Finally, we only found a small impact from LAI and albedo changes on the fire risk (as measured by the fuel moisture index) preceding the Black Summer bushfires, suggesting these biophysical feedbacks did not significantly modulate fire risk. Our results have implications for coupled simulations relying on climatological LAI and albedo, including operation weather and seasonal climate predictions.

Changes in pCO2 and climate paced by grand orbital cycles in the late Cenozoic

As one of the most important greenhouse gases, CO2 is considered a major controlling factor of Earth's climate over geological timescales. However, the origins of quasi-periodic fluctuations in pCO2 on a million-year timescale remain unclear. Here, we used published datasets of atmospheric pCO2, oxygen isotopes of benthic foraminifera (δ18Obenthic) and global mean sea-level (GMSL) from 23 Ma to the present to explore the pacing of pCO2 changes and concomitant climatic effects using multiple time series analysis approaches. Our results indicate that the evolution of late Cenozoic pCO2 and climate was paced by the grand orbital cycles, in particular the ∼4.5 Myr and ∼2.4 Myr eccentricity cycles, and ∼1.3 Myr obliquity cycle. Periodic occurrence of cold conditions was associated with low climate seasonality during the minima of ∼4.5 Myr and ∼2.4 Myr eccentricity cycles. We suggest that cooler conditions are associated with decreased atmospheric pCO2 as a result of higher organic carbon burial due to lower metabolic rate of heterotrophic bacteria and more organic carbon export to the deep ocean. Furthermore, the buildup of glaciers during the minima of grand eccentricity cycles might lower pCO2 via increased ice cover and enhanced dust fluxes. In contrast, high seasonal climate may lead to an opposite effect on atmospheric pCO2 during the maxima of the grand eccentricity cycles. Moreover, we found a distinct shift in the dominant signal from eccentricity to obliquity cycles recorded in the pCO2, δ18Obenthic and GMSL datasets at ∼13 Ma, a time when perennial sea ice occurred in the Arctic and significant ice growth shown in Antarctica. We suggest that the change in the type and distribution of the ice sheets would shift glacial response to orbital forcing and hence mediated global climate and pCO2. Our analysis reveals a clear synchrony among atmospheric pCO2, climate change, and the grand orbital cycles in the late Cenozoic.

Environmental effects of river ice, The Saint John (Wolastoq) River, New Brunswick, Canada

ABSTRACT The Saint John (Wolastoq) River (SJR) is a major international river flowing through the State of Maine, USA, and the Province of New Brunswick, Canada. In terms of river length and basin area, it is one of the largest rivers on the eastern seaboard of North America south of the St. Lawrence River system. Subject to seasonal ice cover, ice conditions vary along the SJR due to natural differences in climate and terrain, and due to anthropogenetic changes, such as the construction of dams. Ice formation, growth, and breakup along the SJR affects its hydraulic and ecological regimes and leads to the potential for ice jamming that has caused severe flooding and ice runs. Ice affects river erosion, flooding, ecology, water quality, and recreational uses of the SJR. An overview of typical winter climate and ice season characteristics along the SJR from Dickey, Maine, USA to Saint John, New Brunswick, and some of its environmental consequences are summarized in this review paper. Ice processes and phenomena that occur along the SJR occur along other northern rivers, and can cause similar environmental concerns and consequences that should not be ignored in river engineering and basin management.

The Added Value of Statistical Seasonal Forecasts

Seasonal climate predictions can assist with timely preparations for extreme episodes, such as dry or wet periods that have associated additional risks of droughts, fires and challenges for water management. Timely warnings for extreme warm summers or cold winters can aid in preparing for increased energy demand. We analyse seasonal forecasts produced by three different methods: (1) a multi-linear statistical forecasting system based on observations only; (2) a non-linear random forest model based on observations only; and (3) process-based dynamical forecast models. The statistical model is an empirical system based on multiple linear regression that is extended to include the trend over the previous 3 months in the predictors, and overfitting is further reduced by using an intermediate multiple linear regression model. This results in a significantly improved El Niño forecast skill, specifically in spring. Also, the Indian Ocean dipole (IOD) index forecast skill shows improvements, specifically in the summer and autumn months. A hybrid multi-model ensemble is constructed by combining the three forecasting methods. The different methods are used to produce seasonal forecasts (three-month means) for near-surface air temperature and monthly accumulated precipitation seasonal forecast with a lead time of one month. We find numerous regions with added value compared with multi-model ensembles based on dynamical models only. For instance, for June, July and August temperatures, added value is observed in extensive parts of both Northern and Southern America, as well as Europe.

Large-scale geographic patterns and environmental and anthropogenic drivers of wetland plant diversity in the Qinghai-Tibet Plateau

BackgroundThe geographic patterns of plant diversity in the Qinghai-Tibet Plateau (QTP) have been widely studied, but few studies have focused on wetland plants. This study quantified the geographic patterns of wetland plant diversity in the QTP through a comprehensive analysis of taxonomic, phylogenetic and functional indices.MethodsBased on a large number of floras, monographs, specimens and field survey data, we constructed a comprehensive dataset of 1,958 wetland plant species in the QTP. Species richness (SR), phylogenetic diversity (PD), functional diversity (FD), net relatedness index (NRI) and net functional relatedness index (NFRI) were used to assess the taxonomic, phylogenetic and functional diversity of wetland plants. We explored the relationships between the diversity indices and four categories of environmental variables (i.e. energy-water, climate seasonality, topography and human activities). We used four diversity indices, namely endemic species richness, weighted endemism, phylogenetic endemism and functional endemism, together with the categorical analysis of neo- and paleo-endemism (CANAPE), to identify the endemic centers of wetland plants in the QTP.ResultsSR, PD and FD were highly consistent and showed a decreasing trend from southeast to northwest, decreasing with increasing elevation. The phylogenetic structure of wetland plant assemblages in most parts of the plateau is mainly clustered. The functional structure of wetland plant assemblages in the southeast of the plateau is overdispersed, while the functional structure of wetland plant assemblages in other areas is clustered. Energy-water and climate seasonality were the two most important categories of variables affecting wetland plant diversity. Environmental variables had a greater effect on the functional structure of wetland plants than on the phylogenetic structure. This study identified seven endemic centres, mainly in the Himalayas and Hengduan Mountains.ConclusionsClimate and topography are the main factors determining the geographic distribution of wetland plant diversity at large scales. The majority of grid cells in the QTP with significant phylogenetic endemism were mixed and super-endemism. At large scales, compared to climate and topography, human activities may not have a negative impact on wetland plant diversity in the QTP.

Aquatic moss δ18O as a proxy for seasonally resolved lake water δ18O, northwest Greenland

Reconstructing past climate seasonality is fundamental to understanding the nature of past climate changes. This is especially true in the Arctic, where climate is intensely seasonal and proxies that can distinguish climate conditions of multiple seasons in a single year are relatively rare. We propose that submerged aquatic mosses, which are abundant subfossils in some Arctic lake sediments and have distinctive seasonal growth morphologies, can be used to estimate past lake water oxygen isotope composition (δ18Olw) across multiple seasons. Aquatic mosses are abundant, well preserved, and grow continuously in Arctic lakes whenever light is available, with some species displaying unique seasonal morphologies influenced by water temperature. Although Greenland paleorecords suggest that aquatic moss oxygen isotope values (δ18Oom) reflect the δ18O values of lake water, no modern calibration between δ18Oom and δ18Olw exists in Greenland. We present a modern δ18Oom vs. δ18Olw calibration using multiple moss species or morphotypes from eight lakes and ponds near Pituffik (Thule), northwest Greenland. We find strong linear relationships (r2 = 0.76-0.85) between the δ18Oom and δ18Olw values of multiple species or morphotypes across the range of relatively low δ18Olw values at Pituffik, and our results indicate isotopic fractionations are similar to those found previously at lower latitudes. To assess the potential of mosses as archives of seasonal δ18Olw values, we analyzed δ18Oom in season-specific segments of moss strands, with seasons identified based upon growth morphology. Moss inferred lake water δ18O values (δ18Olwom) are higher in autumn than spring or summer, likely due to increasing contributions of 18O enriched precipitation and the cumulative effects of lake water evaporation throughout the ice-free season. For moss subsampled throughout summer, δ18Olwom values generally increased through the season in parallel with observed δ18Olw values. Potential temperature dependent fractionation effects during biosynthesis, however, remain unconstrained and should be further addressed with future research. Overall, these findings suggest that aquatic mosses from lake sediments could be used to directly resolve climate seasonality of the past.

Activity patterns of the white-tailed deer (Odocoileus virginianus) in a neotropical dry forest: changes according to age, sex, and climatic season

Activity patterns of the white-tailed deer (Odocoileus virginianus) in a neotropical dry forest: changes according to age, sex, and climatic season

A review for air fermentation to produce the air-based protein

As the worlds population develops, there will be an increasing amount of requirement for food sources, however, traditional agriculture has been limited by many factors, like the availability of new farmland, the support of fertilizer, and the potential pollution of the growing process. Air-based meat provides an ingenious solution to this circumstance. The technology for producing protein uses air as the raw material, which means that regardless of climate conditions or seasons, protein can be produced, and it is produced within a few days rather than months, making air-based protein production gain a higher efficiency. Moreover, this process requires only a small portion of the land used in traditional meat production. However, there are several uncertainties that made this strategy have a hard time to extensively put into effect yet. The data and information in this paper are analyzed and derived from authoritative dissertations and academic websites. This paper will examine this technology from different perspectives to illustrate that advanced strategy in more detail.

Spatio-Temporal Variation in Cyanobacteria and Epiphytic Algae of Thalassia testudinum in Two Localities of Southern Quintana Roo, Mexico

The leaves of Thalassia testudinum provide an ideal substrate for the establishment of small-sized algae with different morphologies that are abundant and diverse. There are few studies on epiphytism in Mexico, and most of them are floristic lists. The objective of this study was to analyze the taxonomic and morphofunctional composition of epiphytes in three climatic seasons, and their relationship with the phorophyte T. testudinum in two localities, El Uvero and Santa Rosa, in the south of Quintana Roo; three transects and fifteen quadrants were set in June and December (2014) and April (2015). A total of 84 epiphytic species were identified: 27 corresponded to Cyanobacteria, 10 to Phaeophyceae, 9 to Chlorophyta, and 38 to Rhodophyta. The highest specific richness was observed in Santa Rosa (73 species). The dry and summer rains seasons share a higher number of species compared to the winter rainy season. The crusty algae Hydrolithon farinosum was the dominant and most persistent species; in addition, filamentous algae presented great specific richness and coverage due to their morphology and reproductive strategies, which allowed them to successfully establish themselves on the phorophyte. This is related to the ecological succession of the epiphytes and seagrass phenology.

Architecture and history of uranium-bearing Palaeocene–Eocene strata deposited on the eastern margin of the Peri-Tethys (Chu-Sarysu Basin, south Kazakhstan)

Deciphering the facies and architecture of alluvial successions provides invaluable insights into the interplay of tectonics, climate, eustasy, and autogenic processes affecting terrestrial sedimentary systems. The stratigraphic response of fluvial systems to variations in discharge and sediment-supply regimes is now well-understood and is tied to changes in climate, precipitation patterns, or sediment sources. The uraniferous Chu-Sarysu Basin in south Kazakhstan occupies the tectonically stable Turan Platform on the eastern margin of the Peri-Tethys, and the study of its Palaeocene–Eocene sedimentary fill offers an opportunity to unravel eustatic and climatic controls that drove the architecture of reservoirs hosting economically important deposits. The stratigraphic succession comprises two multistorey, laterally extensive, sheet-like sandstone bodies floored by prominent erosion surfaces and interpreted as the deposits of channel belts. These packages are interstratified with floodplain, coastal-wetland, and marine-embayment complexes reflecting major extra-channel belt avulsions and marginal-marine incursions on the low-gradient alluvial plain. The stratal architecture was controlled by changes in accommodation likely induced by well-documented sea-level changes in the Peri-Tethys during the Palaeogene, which permitted the development of a chronostratigraphic framework. Eustatic variations culminated in the widespread flooding of the Turan Platform in the middle Eocene, reflected by transgressive lags above a wave ravinement surface capping terrestrial and marginal-marine deposits. Marked changes in fluvial facies, floodplain styles, and inferred channel planforms between Palaeocene and Eocene strata suggest a climatic overprint on river discharge and sedimentation. Upper Palaeocene meandering channel deposits encased in well-drained floodplain strata are indicative of perennial discharge under a semi-arid climate, whereas lower Eocene low-sinuosity channel fills, displaying evidence for transcritical flows and abundant in-situ vegetation, point to intermittent runoff patterns consistent with a humid and seasonal climate. An evolution in atmospheric moisture at the Palaeocene–Eocene boundary from arid to humid conditions has been reported across the Tethys region, and linked to global climatic perturbations of the Palaeocene–Eocene Thermal Maximum.